Download Chem 201 Final Exam: Filling in the Blanks and Balancing Redox Reactions - Prof. Timothy R and more Exams Chemistry in PDF only on Docsity!
Chem 201 Name (PRINT!) KEY
Final Exam December 9, 2008
- (23 pts) Fill in the blank with the best answer.
Hybrid atomic orbitals named sp2 are used by the central atom when it has 3
regions of electron density in the Lewis dot diagram.
An aldehyde would react with dichromate ion to yield the organic functional group called
Carboxylic acid (Be as specific as possible.)
A ketone would react with sodium borohydride to yield the organic functional group
Secondary alcohol (Be as specific as possible.)
63
Cu
2 + has 29 protons, 27 electrons, and 34 neutrons.
T, V, E, and H are examples of state functions, while q and w are
examples of path functions.
The quantum number n is called the primary quantum number; one of the
names of l is the secondary/azimuthal/subsidiary quantum number.
Oxides of metalloids are most likely to dissolve in solution described as
Acidic or basic (acidic/basic/either acidic or basic).
The energy released when a neutral gas phase atom gains an electron is called its
Electron affinity
Of the salts LiF, NaCl. and KBr, the one having the largest value for lattice energy would
be LiF.
- (12 pts) Name the following compounds
Sr 3 (PO 3 ) 2 strontium phosphite
W(ClO 3 ) 3 tumgsten(III)chlorate
Hg 2 (C 2 H 3 O 2 ) 2 mercurous acetate
H 3 AsO 3 (aq) arsenous acid
Chem 201 A Final Exam, p 2 Name
- (6 pts) Give an acceptable name for each of the following
O
OH
pentanoic acid
HO
2-butanol
NH 2
O
propanamide
- (4 pts) Draw the structure (similar to those in #3) for each of the following
methyl butanoate
O
O
cyclohexanone
O
(10 pts) A photon with energy of 2.50 x 10
Joules has
a frequency of:
E
h
2.50x
6.626x
= 3.77 x 10
16 s
a wavelength of:
λ =
c
ν
2.9979x
8 m s
3.77 x
16 s
= 7.95 x
Chem 201 A Final Exam, p 4 Name
- (27 pts) Calculate the values of N, A, and S for each of the following. Then write an
acceptable Lewis dot diagram, using o or x to represent every valence electron. If
resonance occurs, only one of the forms need be shown. Then indicate the electronic
geometry around the central atom, and the overall molecular geometry.
SF 2 N = 24 A = 20 S = 4
Hybrid orbitals for S = sp
Electronic geometry = tetrahedral
Molecular geometry = bent
TeF 5
N = 48 A = 42 S = 6
Hybrid orbitals for Te = sp3d
Electronic geometry = octahedral
Molecular geometry = square pyramidal
IF 4
N = A = S =
Hybrid orbitals for I = sp3d
Electronic geometry = trigonal bipyramidal
Molecular geometry = see-saw
Chem 201 A Final Exam, p 5 Name
- (18 pts) (a) Write the formation reaction of gaseous butane (i.e., the reaction whose
molar enthalpy change is termed
ΔHf
o )
4 C(s) + 5 H 2 (g) = C 4 H 10 (g)
(b) Write the balanced combustion reaction of one mole of butane gas with oxygen gas to
form carbon dioxide gas and liquid water.
C 4 H 10 (g) + 6.5 O 2 (g) = 4 CO 2 (g) + 5 H 2 O(l)
The molar enthalpy change of combustion of butane
ΔHcombustion
o is -2878 kJ/mole.
The
ΔHf
o of carbon dioxide gas is -393.5 kJ/mole, and the
ΔHf
o of liquid water
is -285.83 kJ/mole. Calculate the value of
ΔHf
o for butane gas.
ΔHreaction = Sum ΔH products – Sum of ΔH reactants
-2878 kJ/mole = [4(-393.5 kJ/mol) + 5(-285.83 kJ/mol)] – [ΔHf butane + 6.5 (0)]
ΔHf
o butane gas = +2878 - 3003 = - 125 kJ/mole
2 NaOH(s) + Cu
2+ (aq) = 2 Na
(aq) + Cu(OH) 2 (s)
Chem 201 A Final Exam, p 7 Name
- (25 pts) You must show all your work and prove any assumptions! Showing the
results in the form of a table is strongly encouraged. Assuming complete reaction, how
many moles remain at the end of the reaction for each reactant and each product when
40.00 g of phosphorous, 75.00 g of barium hydroxide, 20.00 g of water, and 15.00 g of
sulfuric acid are reacted according to the reaction:
2 P 4 + 3 Ba(OH) 2 + 6 H 2 O + H 2 SO 4
__
3 BaSO 4 + 6 H 3 PO 2 + 2 PH 3
40.00 g P4(1 mole/123.896g) = 0.3228 mol P
75.00 g Ba(OH)2 (1 mole/171.3416 g) = 0.4377 mole Ba(OH)
20.00 g H2O(1 mole H2O/18.01528 g) = 1.110 mole H2O
15.00 g H2SO4 (1 mol H2SO4/98.0794 g) = 0.1529 mole H2SO
2 P 4 + 3 Ba(OH) 2 + 6 H 2 O + H 2 SO 4
__
3 BaSO 4 + 6 H 3 PO 2 + 2 PH 3
mol inti .3228 .4377 1.110 .1529 0 0 0
mol react 2x 3x 6x x - - -
mol form - - - - 3x 6x 2x
left .3228- .4377- 1.110- .1529-
2x=0 3x=0 6x = 0 x = 0
x=? .1614 .1459 .1850.
L.R.
Left .0310 0 .235 .0070 .4377 .8754.
Chem 201 A Final Exam, p 8 Name
- (16 pts) The electron in a hydrogen atom moved from the n=3 to the n=5 orbit. The
photon associated with this transition is absorbed (absorbed/emitted).
Calculate the wavelength, in nm, of this photon.
€
1
λ
= R H
1
n f
2
1
n i
2
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟
= 1.09737m
-1 1
5
2
1
3
2
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟ = 7.803 x 10
5 m
€
λ =
1
7.803x
5 m
10
9 nm
1 m
⎛
⎝
⎜
⎞
⎠
⎟ =^ 1281 nm
- (16 pts) A cup (heat capacity 15.0 J/K) and the sample of 25.0 g of water (specific
heat 4.18 J/g K) the cup contained were both initially at a temperature of 21.
o C.
A 50.0 g piece of lead, initially at a temperature of 175.
o C, was added to the water and
cup. The final common temperature was 28.
o C. What is the specific heat of lead?
0 = (15.0 J/K)(28.8-21.0deg) + (25.0g)(4.28J/gK)(28.8-21.0deg)
- 50.0g(SpHt)(28.8-175.0deg)
0 = 117 J + 815 J - 7310 g K (SpHt)
SpHt = 0.127 J/gK
